The present invention relates to an analytical shell-model producing apparatus for producing a shell-model for use in analyzing from a solid-state model of a thin-plate structure, and it relates to, in particular, the analytical shell-model producing apparatus, being suitable to be used in a CAE (Computer Aided Engineering) for simulating physical phenomenon by means of numerical values, through the numerical analysis with using a computer.
In the numerical analysis, being represented by, such as, the finite-element method, for example, a model is made up with aggregation of elements, such as, a hexahedron and/or a tetrahedron, for example, as the material to be a target of analyzing (i.e., an analysis target). Also, in a case where the target material of analyzing has a thin-plate structure, a load on computing thereof can be reduced by utilizing a tetragon element and/or a triangle element, to which is given thickness as an attribute value thereof. When using a three(3)-dimensional CAD system, since a material (i.e., a configuration model) was already produced as for the analysis target, therefore even the configuration model of the thin-plate structure is defined to be a solid having thickness.
Conventionally, in a method for producing such a shell-model for use in analyzing from the solid-model of thin-plate structure, as is described in Japanese Patent Laying-Open No. Hei 6-259505 (1994) <JP-A 6-259505>, for example, a thin plate-like configuration portion is designated as the configuration model to be the target of numerical analysis, and then a surface is extracted, which has a geometric feature of being parallel to the surface, among surfaces connecting to the configuration designated. The surfaces, being in parallel with the surface extracted and also being shortest in the distance therebetween, are specified as a pair, and a medial-surface is produced with respect to the pair of surfaces, thereby producing the analysis model.
Also as one of other methods, being described in Japanese Patent Laying-Open No. 2002-207777 (2002) <JP-A 2002-207777>, for example, a hollow mesh model having a two(2)-layer structure is produced for the configuration model to be the target of numerical analysis. And, upon basis of a moving vector set up upon the shape, it is moved while deciding whether a node of the model is in contact with or not, on an element opposing thereto. With this, the nodes of the model are gathered at a neutral point, thereby producing a neutral surface model. However, the neutral surface indicates a surface, being a thin plate-like and located at a neutral position, and it is an equivalent of the shell-model for use in analyzing.
However, in the method for producing the shell-model for use in analyzing, which is described in the Japanese Patent Laying-Open No. Hei 6-259505, for example, since an operator must give an instruction to the thin film-like configuration part, and also only the surface contacting in parallel with the configuration instructed comes to be a target of producing the neutral surface, the operator must give instructions a number of times to that configuration, in particular, if it is a complicated configuration model, and/or a configuration having a rib, for example, and therefore it is not easy to produce the shell model for use in analyzing.
Also, in the method for producing the shell-model for use in analyzing, which is described in the Japanese Patent Laying-Open No. 2002-207777, for example, since the medial-surface model is not produced in the form of the configuration model, but in that of the configuration model, it is necessary to re-produce the configuration model from the mesh data when changing the configuration, such as, for the purpose of parameter survey, etc. Also, sometimes there are cases where the configuration model cannot be produced if trying to produce it again, since the configuration is too complicated.